Process for preparing heterocyclic carbenes

ABSTRACT

A process for preparing heterocyclic carbenes of the ##STR1## in which R 1 , R 2 , R 3  and R 4  are individually saturated or unsaturated, straight chain, branched or cyclic, unsubstituted or substituted C 1  -C 10  alkyl, C 2  -C 5  alkylidene, C 2  -C 5  alkylidine, C 7  -C 19  aralkyl or C 6  -C 14  alkyl groups, R 3  and R 4  can also stand for hydrogen or form jointly anellated, substituted or unsubstituted groups with between 3 and 7 carbon atoms and X stands for carbon or nitrogen, R 3  being dropped if X is nitrogen comprising reacting azolium salts with a deprotonizing reagent in pure liquid ammonia or in pure organic amine or a mixture of liquid ammonia or an organic amine and an organic polar-aprotic solvent which are a plurality of temperature-sensitive carbenes are produced under mild reaction conditions at temperatures of between -75 and 0° C.

This application is as 371 of PCT/EP97/01296 filed Mar. 14, 1997.

Heterocyclic carbenes have in recent times been found to be useful ascomplexing ligands for a wide variety of metals, with the correspondingmetal complexes having a high thermal and chemical stability and verygood catalyst properties in the homogeneous catalysis of variousreactions.

Metal complexes of metals of metals of the 8th, 9th and 10th groups ofthe Period Table containing heterocyclic monocarbenes or dicarbenes asligands are described, for example, in the European Patent ApplicationNo. 0 719 753 as suitable catalysts for reactions leading to theformation of carbon-carbon, carbon-hydrogen and carbon-silicon bonds.Furthermore, in the German Patent Application number P 44 47 067.3,cobalt or rhodium complexes having heterocyclic monocarbene or dicarbeneligands are used as catalysts for the hydroformylation of olefinicallyunsaturated compounds to give aldehydes.

According to the European Patent Application 0 719 758, it is alsopossible to prepare aromatic olefins from haloaromatics and olefins viaa Heck reaction in the presence, as catalysts, of palladium complexescontaining heterocyclic carbenes as ligands.

Furthermore, the German Patent Application number P 44 47 070.3discloses the use of complexes of the lanthanides having heterocycliccarbenes as complexing ligands as catalysts for reactions which arecatalyzed by Lewis acids, e.g. for preparing polylactides, and forvarious CH, CC, CSi and NC linkage reactions.

Metal complexes of heterocyclic carbenes thus have a wide range ofcatalytic applications; the synthesis of these compounds is therefore ofgreat importance. On this subject, one is frequently directed to thefree heterocyclic carbenes whose preparation has, however, hitherto beentied to very specific reaction conditions which greatly restrict thevariety of classes of materials which can be used as starting material.Thus, according to the known synthetic methods, only a comparativelysmall selection of heterocyclic carbenes has hitherto been obtainable,in particular 1,3-dimethylimidazolin-2-ylidene and1,3-bis(adamantyl)imidazolin-2-ylidene.

The process for preparing free heterocyclic carbenes of the imidazoletype described in J. Am. Chem. Soc. 1991, 113, pp. 361-63 comprisesreacting an imidazolium salt with a deprotonation reagent in a polaraprotic solvent at relatively high temperatures.

The deprotonation reagent used here is sodium hydride in the presence ofcatalytic amounts of dimethyl sulfoxide (DMSO) or potassiumtert-butoxide; the polar aprotic solvent used is tetrahydrofuran (THF).

The work-up of a free carbene prepared in this way is usually carriedout by filtering off the precipitated salts, removing the solvent underreduced pressure and distilling or subliming the residue containing thecarbene in a high vacuum at relatively high temperatures. This procedurehas the disadvantage that the frequently temperature-sensitive freecarbenes are subjected during the purification to a thermal stress whichleads to the formation of downstream products and thus to losses inyield. In addition, for reasons of solubility and/or volatility, only avery small selection of carbenes is obtainable in good yield and in pureform, in particular in the case of oily imidazolium salts and theircarbene products. A further disadvantage is that in the known procedurethe deprotonation rate using the customary reagents and solvents is low,in particular at the relatively low temperatures which are desirable forthe stability of the carbenes formed. If the higher temperaturesactually required for the deprotonation are employed, the carbenesformed decompose completely or partially even at room temperature. Thisis compounded by the fact that most polar aprotic solvents such as DMSOor acetonitrile can only be obtained in anhydrous form with aconsiderable outlay in terms of apparatus and money. In addition,restrictions are placed on the solvents used in terms of their acidity;thus, nitromethane is unsuitable as solvent because of its relativelyhigh acidity, although it has good solvent properties for the azoliumsalts.

The comparatively high boiling points of most polar aprotic solvents(e.g. 189° C. for DMSO) are also disadvantageous in that the individualreaction components cannot be separated completely from one another.This likewise leads to a reduction in yield and to the formation ofimpure products. This procedure is particularly disadvantageous ifdownstream products of metal complexes are to be prepared in goodyields, i.e. the free carbene is to be prepared from the imidazoliumsalt and reacted in a single-vessel process with metal-containingcomponents (e.g. metal halides and acetylacetonates) to givemetal-carbene complexes.

It is therefore an object of the invention to provide a generallyuseable process for preparing free heterocyclic carbenes which avoidsthe many disadvantages mentioned for known processes and makes itpossible to prepare the carbenes in a simple manner at a high conversionand in a high selectivity.

This object is achieved by a process for preparing heterocyclic carbenesof the formula I ##STR2## where R¹, R², R³ and R⁴ are identical ordifferent and are saturated or unsaturated, straight-chain, branched orcyclic, unsubstituted or substituted C₁ -C₁₀ -alkyl, C₂ -C₅ -alkylidene,C₂ -C₅ -alkylidyne, C₇ -C₁₉ -aralkyl or C₆ -C₁₄ -aryl radicals, R³ andR⁴ can also be hydrogen or together form fused-on, substituted orunsubstituted radicals having 3-7 carbon atoms, X is carbon or nitrogen,with R³ not being present when X is nitrogen,

by reacting azolium salts of the formula II ##STR3## where R¹, R², R³and R⁴ are as defined for the formula I and A⁻ is a halide,pseudohalide, borate, phosphate, carboxylate or metal complex ion,

with a deprotonation reagent in pure liquid ammonia or in pure organicamine or in a mixture of liquid ammonia or an organic amine and anorganic polar aprotic solvent.

The process of the invention makes it possible to deprotonate azoliumsalts of the formula II under surprisingly mild reaction conditions. Thereaction temperature is in the range from -75 to 0° C., preferably inthe range from -50 to -20° C. and in particular from -50 to -30° C. Itis here of decisive importance that the solvent used for the reaction ispure liquid ammonia or a pure organic amine or a mixture of liquidammonia or an organic amine and an organic polar aprotic solvent. Ifpure liquid ammonia is used, the reaction temperature is from -75 to-35° C.

Organic polar aprotic solvents which can be used are, for example,tetrahydrofuran, dimethyl sulfoxide or acetonitrile, with the volumeratio of ammonia or organic amine to the polar aprotic solvent beingfrom 1:0.01 to 1:100, preferably from 1:0.1 to 1:10 and in particular1:0.2. Organic amines which can be used are primary C₁ -C₄ -alkylamineswhich are liquid at the reaction temperature, in particular methylamineor ethylamine.

Deprotonation reagents used are strong bases such as metal hydrides,metal amides, metal alkoxides, metal carboxylates, carbonylmetallates orhydrido(carbonyl)metallates. Preference is given to using alkali metalhydrides such as sodium hydride or alkali metal amides such as potassiumamide. Based on the azolium salt of the formula II to be deprotonated,the deprotonation reagent is used in at least the stoichiometric amount,preferably in a 10% molar excess.

The reaction of the azolium salts of the formula II with thedeprotonation reagent is carried out under strict exclusion of air andmoisture by addition of the deprotonation reagent to the solution of theazolium salt in pure ammonia, in pure organic amine or in a mixture ofammonia or an organic amine and the organic polar aprotic solvent. Thereaction proceeds at a high rate and is often essentially complete aftera few minutes. However, to complete the reaction, it is advisable toadhere to reaction times of up to one hour. The reaction mixtureobtained is first filtered to remove the precipitated metal salts. Thefiltered solution of the free carbene can be used without furtherwork-up for downstream reactions, for example metal complex formation.When carrying out the deprotonation in a mixture of ammonia or anorganic amine and a polar aprotic solvent, the ammonia or the organicamine may, if desired, be removed by evaporation before furtherprocessing of the carbene. In addition, any metal salts still present insmall amounts are subsequently removed completely by filtration ordecantation, advantageously with lowering of the temperature.

If the free carbene is to be isolated as a pure substance, i.e. free ofsolvent, the polar aprotic solvent and/or the organic amine is removedunder reduced pressure. This is possible in a gentle manner atrelatively low temperatures because the solvents used according to theprocess of the invention have relatively low boiling points.

If the deprotonation is carried out in pure ammonia, this can easily becompletely removed from the reaction system either by increasing thetemperature above the boiling point or at very low temperatures in therange from -50 to -100° C. by reducing the pressure, if desired by thetechnique of vacuum freeze drying.

Liquid ammonia has the advantage that it is miscible in all proportionswith many organic solvents, it has a high solvent capability for organicsalts, aromatic compounds and polar functional groups and isproton-inactive. The azolium salts used as starting materials dissolvebetter in pure ammonia and in mixtures of ammonia and a polar aproticsolvent than in the organic polar aprotic solvent itself.

A further advantage of liquid ammonia or its solutions with organicpolar aprotic solvents is that freedom from water can be achieved in asimple manner, which is of particular importance for the stability ofthe resulting carbenes. Surprisingly, the heterocyclic carbenes preparedaccording to the process of the present invention are inert towardammonia.

In addition, ammonia is a particularly inexpensive and nonhazardoussolvent which does not absolutely have to be recycled.

The process of the invention can be applied to many azolium salts havingthe formula II where R¹, R², R³ and R⁴ are identical or different andare saturated or unsaturated, straight-chain, branched or cyclic,unsubstituted or substituted C₁ -C₁₀ -, preferably C₁ -C₆ -alkyl, C₂ -C₅-, preferably C₂ -C₄ -alkylidyne, C₂ -C₅ -, preferably C₂ -C₄-alkylidyne, C₇ -C₁₉ -, preferably C₇ -C₁₀ -aralkyl or C₆ -C₁₄ -arylradical, preferably a phenyl radical, R³ and R⁴ can also be hydrogen ortogether form fused-on substituted or unsubstituted radicals having 3-7,preferably 4, carbon atoms, X is carbon or nitrogen, with R³ not beingpresent when X is nitrogen.

The radicals R¹, R², R³ and R⁴ can each bear one or more substituentssuch as amine, nitro, nitrile, isonitrile, ether, alcohol, aldehyde orketone groups, carboxylic acid derivatives, in particular esters oramides, halogenated, in particular fluorinated or perfluorinated,hydrocarbon radicals, carbohydrate, phosphine, phosphine oxide,phosphine sulfide, phosphole radicals, phosphite derivatives, aliphaticor aromatic sulfonic acid derivatives, their salts, esters or amides,silyl functions, boryl groups or heterocyclic substituents. Preferably,one of the two radicals R¹ or R² has a heterocyclic substituent such asa pyridine ring or azolium salts.

The anion A⁻ in the formula II is preferably a tetraphenylborate,tetrafluoroborate, hexafluorophosphate, acetate, tetracarbonylcobaltate,hexafluoroferrate (III), tetrachloroferrate(III), tetrachloroaluminateor tetrachloropalladate(II) ion.

The process of the invention makes it possible to prepare manypreviously unknown free carbenes in high yield and purity in very shortreaction times. This is attributable, on the one hand, to the greatstructural variety of available azolium salts of the formula II and, onthe other hand, to the mild and efficient deprotonation conditions whichare surprisingly made possible by the solvents used. The process of theinvention has therefore been found to be particularly useful forpreparing thermally sensitive carbenes. Chiral and immobilized carbenesare also obtainable for the first time in this way. Owing to the simplereaction procedure, the process is also suitable for industrial use.

In view of the fact that the heterocyclic carbenes of the formula I arewater-sensitive and ammonia has water-like properties, it is surprisingto a person skilled in the art that the free heterocyclic carbenes arecompletely stable toward ammonia and that such high deprotonation rateshave been found for the azolium salts of the formula II.

EXAMPLES General Example for the preparation of 1,3-disubstitutedimidazolin-2-ylidenes according to the following equation ##STR4##

The apparatus for preparing the temperature-, air- andmoisture-sensitive imidazolin-2-ylidenes comprises a condensation vesselfitted with gas inlet tube and overpressure valve for drying andpurifying the ammonia plus a graduated reaction vessel which is equippedwith a dry ice condenser and further devices for adding or taking outsolvents, solutions and solids. The condensation vessel and the actualreaction vessel are connected to one another via a condensation bridgehaving two taps or another vacuum-resistant line.

The reaction vessel is charged under strict exclusion of air andmoisture with 10 mmol of an azolium salt in 15 ml of a polar aproticsolvent such as THF. At about -70° C., 75 ml of ammonia (purity 99.8%)are condensed under reduced pressure into the condensation vessel whichcontains about 2 g of potassium, forming a deep blue solution.

Subsequently, the ammonia is condensed under reduced pressure via thecondensation bridge into the actual reaction vessel. This vesselcontains the suspension of the imidazolium salt to be deprotonated inTHF. For this purpose, the condensation vessel is warmed gently whilethe reaction vessel and the dry ice condenser are cooled to about -70°C. by means of dry ice/acetone. The pressure in the apparatus is thenequilibrated using inert gas.

11 mmol of the deprotonation reagent NaH are then added under an inertgas atmosphere and the cooling under the reaction vessel is removed.Granulated NaH is advantageously used. A clear colorless, occasionallysomewhat yellowish solution is formed within one hour. After thereaction is complete, the ammonia is allowed to vaporize at atmosphericpressure or it is condensed under reduced pressure into the condensationvessel or into cold traps. After the ammonia has been removed completelyfrom the reaction vessel, the resulting THF solution of the heterocycliccarbene is, to remove the sodium halide formed, made up with THF ortoluene to a total volume of 30 ml and filtered. The carbene solutionsthus produced are spectroscopically pure and can be employed withoutfurther purification in downstream reactions.

In the following examples, the preparation of the correspondingimidazolium salts is described first. The free carbenes are producedtherefrom according to the above equation. The free carbenes arecharacterized by reacting them with suitable transition metal precursorsto give transition metal-carbene complexes and/or by ¹ H- and ¹³ C-NMRspectroscopy of the free carbenes and of the oxidation products afterreacting the free carbenes with elemental sulfur.

Example 1 1,3-dimethylimidazolin-2-yliden (1)

A) Preparation of 1,3-dimethylimidazolium diiodide (1a)

21.3 ml (267 mmol) of N-methylimidazole are dissolved in 150 ml ofisopropanol. After addition of 17.3 ml (280 mmol) of methyl iodide, themixture is heated at the boiling point for 8 hours. After cooling, thesolution is allowed to stand for 12 hours to crystallize. Thecrystalline 1,3-dimethylimidazolium iodide (1a) is filtered off andwashed with 50 ml of diethyl ether and 50 ml of THF. Yield: 57 g (96%).

¹ H-NMR (400 MHz, CDCl₃, δ in ppm): 8.97 (s, NCHN); 7.10 (s, NCH₂ CH₂N); 3.46 (s, CH₃); ¹³ C-NMR (100.6 MHz, CDCl₃, ppm): 134.7 (s, NCHN);121.85 (s, NCH₂ CH₂ N); 35.29 (s, CH₃).

B) Preparation of 1,3-dimethylimidazolin-2-ylidene (1)

10 mmol of 1,3-dimethylimidazolium iodide (1a) are deprotonated in 75 mlof NH₃(liq) /15 ml of THF by means of 11 mmol of NaH as described in thegeneral example. Removing the ammonia under reduced pressure gives acolorless spectroscopically pure solution of1,3-dimethylimidazolin-2-ylidene (1) in THF which is, to remove thesodium iodide, made up with toluene to a total volume of 40 ml andsubsequently filtered. The filtrate is used without further purificationfor the synthesis of the complex.

¹³ C-NMR (100 MHz, THF, d₈ -THF external reference, δ in ppm): 215.1 (s,NCN): 120.6 (s, NCH₂ CH₂ N); 36.2 (s, CH₃);

C) Preparation of chloro(η⁴-1,5-cyclooctadiene)(1,3-dimethylimidazolin-2-ylidene)rhodim (I)

247 mg (0.5 mmol) of bis[(μ-chloro)(77⁴ -1,5-cyclooctadiene)rhodium] aredissolved at room temperature in 20 ml of absolute THF and admixed with192 mg (1 mmol) of 1,3-dimethylimidazolin-2-ylidene. The mixture isstirred for a further 15 minutes at room temperature, the solvent isremoved under reduced pressure and the residue is purified by washingwith 10 ml of diethyl ether. Yield: 310 mg (91%).

Elemental analysis (C₁₃ H₂₀ ClN₂ Rh) (in % by weight): calculated: C45.57 H 5.88 N 8.17 found: C 45.63 H 5.98 N 8.35.

¹ H-NMR (400 MHz, CDCl₃, 20° C., δ in ppm): 6.8 (s, 2H, CHCH); 4.1 (s,6H, NCH₃), 5.0 (2H); 3.3 (2H); 2.4 (4H); 1.9 (4H) (cyclooctadiene);

¹³ C{¹ H}-NMR (100 MHz, CDCl₃, δ in ppm): 182.6 (d, NCN, ¹ J(C--Rh)=50Hz); 121.9 (CH₂ CH₂); 37.6 (NCH₃); 98.5; 67.7; 33.0; 28.9(cyclooctadiene).

Example 2 1,1'-(1,2-ethylene)-3,3'-dimethyldiimidazolin-2,2'-diylidene(2)

A) Preparation of 1,1'-(1,2-ethylene)-3,3'-dimethyldiimidazoliumdibromide (2a)

5 ml (58 mmol) of 1,2-dibromethane, 9.25 ml (116 mmol) ofN-methylimidazole and 10 ml of methanol as solvent are heated at atemperature of 80° C. for two hours. After cooling, the solvent isremoved under reduced pressure. This gives 18.5 g (92%) of a white solidwhich represents the desired product (2a).

¹ H-NMR (400 MHz, CDCl₃, δ in ppm): 9.29 (NCHN); 7.77 (CHCH), 4.77 (NCH₂CH₂ N); 3.85 (NCH₃);

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 137.1 (NCHN); 123.7; 122.8 (CHCH);48.2 (NCH₂ CH₂ N); 36.0 (NCH₃).

B) Preparation of1,1'-(1,2-ethylene)-3,3'-dimethyldiimidazolin-2,2'-diylidene (2).

10 mmol of the diimidazolium salt (2a) are deprotonated using 22 mmol ofNaH in NH₃ /THF in a volume ratio of 5:1 as described in the generalexample. Removing the ammonia gives a spectroscopically pure solution ofthe dicarbene in THF.

¹³ C-NMR (100 MHz, THF, 10° C., δ in ppm): 215.9 (NCN); 120.3; 119.7(NCHCHN); 52.7 (CH₂ N); 37.7 (NCH₃).

C) Preparation of[1,1'-(1,2-ethylene)-3,3'-dimethyldiimidazolin-2,2'-diylidene]bis[chloro(.eta.⁴-1,5-cyclooctadiene)rhodium(I)]

247 mg (0.5 mmol) of bis[(μ-chloro)(η⁴ -1,5-cyclooctadiene)rhodium] aredissolved at room temperature in 20 ml of absolute THF and admixed with190 mg (1 mmol) of1,1'-(1,2-ethylene)-3,3'-dimethyldiimidazolin-2,2'-diylidene (2). Themixture is stirred for 3 hours at room temperature, the solvent isremoved under reduced pressure and the product is purified by washingwith 10 ml of diethyl ether. The product is dissolved in 10 ml ofmethylene chloride and covered with a layer of 20 ml of pentane. Thesolvent mixture is decanted from the resulting crystals and the crystalsare dried under reduced pressure. The pale yellow crystals are readilysoluble in chloroform and methylene chloride. Yield: 80 mg (18%).

¹ H-NMR (400 MHz, CDCl₃, 20° C., δ in ppm): 6.85 (d, 2H, J=1.9 Hz), 6.47(d, 2H, J=1.9 Hz, NCH), 4.01 (s, 6H, NCH₃), 4.73 (m, 4H, CH₂ CH₂); 3.34(m, 4H); 3.22 (m, 4H); 2.44 (m, 4H); 2.00 (m, 4H), 5.17 (m, 4H); 4.98(m, 4H, cyclooctadiene).

¹³ C-NMR (100 MHz, CDCl₃, 20° C., δ in ppm: 181.3 (d, ¹ J_(C-Rh)) =50.5Hz, NCN); 123.9; 120.6 (NCH); 37.8 (NCH₃); 50.9 (CH₂ CH₂), 69.2 (d, ¹J.sub.(C-Rh) =14.6 Hz), 67.8 (d, ¹ J.sub.(C-Rh) =14.5 Hz); 29.5; 28.4(cyclooctadiene);

Elemental analysis (C₂₆ H₂₈ Cl₂ N₄ Rh₂ *CH₂ Cl₂) (in % by weight):Calculated: C 42.21 H 5.25 N 7.29 Found: C 43.02 H 5.41 N 7.31.

Example 3 N,N'-1,3-Di(n-hexyl)imidazolin-2-ylidene (3)

A) Preparation of N,N'-1,3-di(n-hexyl)imidazolium bromide (3a)

1st stage: Preparation of the potassium imidazolide C₃ H₃ N₂ K

4 g (100 mmol) of potassium are added to 100 ml of toluene and heated at80-100° C. until the potassium has melted to form small spheres. Themixture is cooled slowly to about 40° C., 7.5 g (110 mmol) of imidazoleare added a little at a time and the mixture is heated again. A whiteprecipitate forms and gas is evolved. When the addition of the imidazolehas been completed, the mixture is heated for 2 hours at boiling pointand is allowed to cool. The white precipitate is filtered off and dried.Yield: 10.3 g (97%).

¹ H-NMR (400 MHz, 25° C., CDCl₃, δ in ppm): 7.72 (s,1), 7.02 (s,2).

2nd Stage: Preparation of monoalkylated N-(n-hexyl)imidazole

4 g (37 mmol) of potassium imidazolide are suspended in 100 ml oftoluene. 6.0 ml (42 mmol) of 1-bromohexane are added, the mixture isheated while stirring to 110° C., this temperature is maintained for 5hours and the mixture is then cooled slowly. The potassium bromideformed is filtered off and the toluene is partially removed underreduced pressure. The product remains in the form of a clear, slightlyyellowish liquid. Yield: 5.2 g (93%).

¹ H-NMR (400 MHz, 25° C., CDCl₃, δ in ppm): 7.91(d,2), 7.83(s,1),3.79(t,2), 1.86(m,2), 1.82(m,2), 1.65(m,2), 1.53(m,2), 1.48(m,3).

3rd Stage: Preparation of the dialkylatedN,N'-(1,3-di(n-hexyl)imidazolium bromide (3a)

5.2 g (34 mmol) of N-(n-hexyl)imidazole are dissolved in 100 ml oftoluene and admixed with a further 5.6 ml of 1-n-hexyl bromide. Themixture is heated while stirring for 3 hours at 110° C. and is thenallowed to cool. The oily product is produced with formation of a secondphase. The toluene is removed under reduced pressure. Yield: 10.0 g(92%).

¹ H-NMR (400 MHz, 25° C., C₆ D₆, δ in ppm): 9.24(s,1), 7.52(s,2),4.23(t,4), 1.90(m,4), 1.35(m,12), 0.9(m,6).

¹³ C-NMR (100 MHz, 25° C., C₆ D₆, δ in ppm): 137.50, 123.27, 50.42,31.70, 30.48, 26.31, 23.06, 14.16.

B) Preparation of N,N'-1,3-di(n-hexyl)imidazolin-2-ylidene (3)

The preparation is carried out as described in the general example andgives a spectroscopically pure solution of 10 mmol ofN,N'-1,3-di(n-hexyl)imidazolin-2-ylidene in 40 ml of THF.

C) Preparation ofpentacarbonyl[1,3-di-(n-hexyl)imidazolin-2-ylidene)tungsten

3 mmol of a carbene solution of di-n-hexylcarbene (set free as describedin the general example from the salt N,N'-(1,3-di(n-hexyl)imidazoliumbromide prepared under Point A)) are added to a solution of 1 g (2.8mmol) of hexylcarbonyltungsten in 50 ml of THF. A yellow solid isformed. Yield: 1.31 g (82%).

¹³ C-NMR (100 MHz, 25° C., C₆ D₆, δ in ppm): 198.69, 122.37, 53.22,31.50, 30.85, 27.61, 23.05, 14.18.

D) Preparation of 1,3-di(n-hexyl)imidazoline-2-thione

A carbene solution of di-n-hexyl carbene (set free by the ammonia routefrom the salt N,N'-(1,3-di(n-hexyl)imidazolium bromide prepared underPoint 2) is added to a solution of 0.2 g (5.5 mmol) of flowers ofsulfur. A yellow solid precipitates. Yield: 1.40 g (95%).

¹³ C-NMR (100 MHz, 25° C., CDCl₃, δ in ppm): 189.65, 124.21, 52.67,36.29, 34.03, 31.17, 27.65, 19.12.

Example 4 N,N'-1,3-Di(1H,1H,2H,2H-tridecafluorooctyl)imidazole-2-ylidene(4)

A) Preparation of N,N'-1,3-di(1H,1H,2H,2H-tridecafluorooctyl)imidazoliumiodide (4a)

Preparation of the monoperfluoroalkylated ligand precursorN-(1H,1H,2H,2H-tridecafluorooctyl)imidazole

2 g (18.5 mmol) of potassium imidazolide (cf. Example 3A) are suspendedin 100 ml of toluene. 5.2 ml (21 mmol) of 1H,1H,2H,2H-tridecafluorooctyliodide are added, the mixture is heated while stirring for 16 hours at110° C. and then cooled slowly. The potassium iodide formed is filteredoff and the toluene is removed under reduced pressure. This leaves theproduct in the form of a clear, slightly yellowish liquid. Yield: 6.0 g(79%).

¹ H-NMR (400 MHz, 25° C., CDCl₃ δ in ppm): 7.86(s,1), 7.67(s,1),7.09(s,1), 4.42(t,2), 2.72(n,2).

¹³ C-NMR (100 MHz, 25° C., C₆ D₆, δ in ppm): 135.07, 121.27, 118.59,46.42, 38.78, 36.82, 36.61, 35.85, 33.01, 32.73, 32.19.

Preparation of the doubly perfluoroalkylatedN,N'-1,3-di(1H,1H,2H,2H-tridecylfluorooctyl)imidazolium iodide

6.0 g (14 mmol) of N-(1H,1H,2H,2H-tridecafluorooctyl)imidazole aredissolved in 100 ml of toluene and admixed with a further 3.6 ml (15mmol) of 1H,1H,2H,2H-tridecafluorooctyl iodide. The mixture is thenheated while stirring for 12 hours at 110° C. and then allowed to cool.The toluene is removed under reduced pressure. The resulting product isa viscous resin. Yield: 9.6 g (78%).

¹ H-NMR (400 MHz, 25° C., C₆ D₆, δ in ppm): 9.24(s,1), 7.52(s,2),4.74(t,4), 2.91(m,4).

¹³ C-NMR (100 MHz, 25° C., CDCl₃, δ in ppm): 138.4, 119.2, 47.5, 39.7,35.0, 36.8, 36.3, 35.6, 34.1, 32.7, 32.4.

B) Preparation ofN,N'-1,3-di(1H,1H,2H,2H-tridecafluorooctyl)imidazolin-2-ylidene (4)

The preparation is carried out from (4a) as described in the generalexample and gives a solution of 10 mmol of the free, spectroscopicallypure carbene (4) in 40 ml of THF.

¹³ C-NMR (100 MHz, 25° C., THF, δ in ppm): 214.5, 117.5, 67.5, 59.0,36.9, 36.2, 35.7, 34.2, 32.7, 32.5.

Example 5 1,3-Dicyclohexylimidazolin-2-ylidene (5)

A) Preparation of 1,3-dicyclohexylimidazolium chloride (5a)

A 500 ml round-bottom flask is charged with 9.92 g (100 mmol) ofcyclohexylamine in 100 ml of toluene. 30 g (100 mmol) ofparaformaldehyde are added while stirring vigorously. After 30 minutesat room temperature, the flask is cooled to 0° C. using an ice bath anda further 9.92 g (100 mmol) of cyclohexylamine are added. While coolingand stirring vigorously, 30 ml (100 mmol) of a 3.3 molar HCl solutionare then slowly added dropwise. The cooling is then removed, 145 ml (100mmol) of 40% strength aqueous glyoxal solution are slowly added and thereaction mixture is stirred overnight at 50° C.

For the work-up, 100 ml of ether and 50 ml of saturated sodium carbonatesolution are added. If necessary, the emulsion which forms is broken byaddition of a little pentane. The ether phase is separated off, theaqueous phase is washed three times with 100 ml each time of ether andthe volatile constituents are removed under reduced pressure. Theresidue is extracted with 150 ml of dichloromethane, dried over MgSO₄and filtered.

Removal of the solvent under reduced pressure leaves a bulky foam whichis washed with ether and can then be broken up to give a whitehygroscopic powder. Yield 23.5 g (75%).

¹ H-NMR (400 MHz, 25° C., CDCl₃, δ in ppm): 10.43 (s, 1H, N₂ C--H), 7.41(m, 2H, C--H), 4.33 (m, 1H, R₃ C--H), 1.0-2.0 (overlapping multiplets,20H, cyclohexyl-CH₂).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 134.9 (N₂ C--H), 119.7 (C--H), 59.3(H--CR₃), 33.1 (CH--CH₂), 24.5 (2CH₂), 24.2 (CH₂).

Mass spectrum (FAB): m/e=501.4 ([ME⁺ +M-Cl], 6.4), 233 ([M⁺ -Cl], 100).

B) Preparation of 1,3-dicyclohexylimidazolin-2-ylidene (5)

2.68 g (10 mmol) of 1,3-dicyclohexylimidazolium chloride (5a) aredeprotonated in accordance with the general description in a mixture of20 ml of THF and 100 ml of NH₃ using 260 mg (10.8 mmol) of NaH. Avirtually colorless solution of 1,3-dicyclohexylimidazolin-2-ylidene (5)is formed. After removing the ammonia, the mixture is made up with THFto 40 ml and the solution thus obtained is used further without furtherwork-up.

¹³ C-NMR (100 MHz, THF, CD₃ NO, δ in ppm): 210.1 (C:), 115.7 (C═C), 66.8(N--CH), 59.6 (2CH₂), 34.9 (2CH₂) 25.9 (CH₂).

C) Preparation ofpentacarbonyl(1,3-dicyclohexylimidazolin-2-ylidene)tungsten (5b)

A Schlenk tube is charged with 880 mg (2.5 mmol) of hexacarbonyltungstenin 100 ml degassed THF. While stirring 10 ml (2.5 mmol) of 0.25 Mcarbene solution (5) are then added dropwise under a protective gasatmosphere and the reaction mixture is stirred for a few hours. Thesolvent is then removed under reduced pressure and anyhexycarbonyltungsten still present is sublimed off overnight at roomtemperature.

The residue is dissolved in methylene chloride and filtered. Afterconcentrating the mother liquor, the product (5b) can be obtained byslow cooling in the form of yellow crystals. Yield: 854 mg (61%).

¹ H-NMR (400 MHz, CDCl₃ δ in ppm): 7.00 (s, 2H, N--CH═), 4.75 (m, 2H,N--CH), 1.98 (m, 4H, CH₂), 1.87 (m, 4H, CH₂ ), 1.75 (m, 2H, CH₂), 1.45(m, 8H, CH₂), 1.24 (m, 2E, CH₂).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 201.5 (J(¹⁸³ W--¹³ C)=126 Hz,W--CO), 197.7 (J(¹⁸³ W--¹³ C)=126 Hz, W--(CO)₄), 176.4 (J(¹⁸³ W--¹³C)=99 Hz, W--CN₂), 118.34 (C═C), 61.7 (N--CH), 34.4 (CH-CH₂), 25.5(CH₂), 25.1 (CH₂ (C₂ H₄)₂).

Mass spectrum (CI): m/e=556 ([M⁺, 22), 528 ([M⁺ -CO], 6), 233 ([M⁺-W(CO₅)], 100).

Elemental analysis (in % by weight): Calculated: C 43.18 H 4.3 N 5.0Found: C 43.17 H 4.46 N 5.04.

D) Preparation of chloro(η⁴-5-cyclooctadiene)(1,3-dicyclohexylimidazolin-2-ylidene)rhodium (5c)

A Schlenk tube is charged with 200 mg (0.4 mmol) of bis[(μ-chloro)(η⁴-1,5-cyclooctadiene)rhodium] in 5 ml of THF. 3.3 ml (0.8 mmol) ofcarbene solution (5) are slowly added to this solution.

The reaction mixture is stirred further for one hour at roomtemperature, the solvent is then taken off, the residue is taken up inmethylene chloride and filtered. The complex is precipitated by additionof pentane and subsequently washed with pentane. Removal of the volatileconstituents under reduced pressure gives the complex as a yellowpowder. Yield: 325 mg (85%).

¹ H-NMR (400 MHz, CDCl₃, δ in ppm): 6.78 (s, 2H, NCH═), 5.27 (m, 2H,COD--CH), 4.93 (m, 2H, N--CH), 3.23 (m, 2H, COD--CH), 2.31 (m, 4H,COD--CH₂), 1.89 (m, 4H, COD--CH), 1.91-1.15 (overlapping multiplets,22H, cyclohexyl-CH₂).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 180.1 (d, J(Rh--¹³ C)=51 Hz),Rh--CN₂), 117.5 (N--CH═), 97.8 (d, J(Rh--¹³ C)=3 Hz), COD--CH), 97.7 (d,J(Rh--¹³ C)=3 Hz), COD--CH), 67.5 (d, J(Rh--¹³ C)=14 Hz, COD--CH), 60.6(N--CH), 34.5 (COD--CH₂), 34.4 (cyclohexyl-CH₂), 33.4 (cyclohexyl-CH₂),29.2 (COD--CH₂), 26.4 (cyclohexyl-CH₂), 26.1 (cyclohexyl-CH₂), 25.7(cyclohexyl-CH₂).

Example 6 1-Methyl-3-(2-phenylethyl)imidazolin-2-ylidene (6)

A) Preparation of 1-methyl-3-(2-phenylethyl)imidazolium chloride (6a)

5.0 ml (62.7 mmol) of N-methylimidazole are heated together with 8.23 ml(8.82 g; 62.7 mmol) of 1-chloro-2-phenylethane without addition of asolvent for 18 hours at 140° C. After cooling, the resulting1-methyl-3-(2-phenylethyl)imidazolium chloride (6a) is allowed to standto crystalize.

¹ H-NMR (400 MHz, D₂ O, δ in ppm): 8.23 (s, NCHN); 7.0-7.2 (m, 5H, Ph);6.9 (2H, NCHCHN); 4.32 (2H, NCH₂), 3.6 (3H, NCH₃), 2.95 (2H, CH₂ Ph).

¹³ C-NMR (100 MHz, D₂ O, ppm): 137.04 (s, NCHN); 136.11; 135.96; 129.17;129.00; 127.48; 123.75; 123.66 (Ph--C); 122.43; 122.34 (NCHCHN); 50.91(NCH₂); 35.82 (s, CH₃); 35.75 (CH₂ Ph).

B) Preparation of 1-methyl-3-(2-phenylethyl)imidazolin-2-ylidene (6)

As described in the general example, 10 mol of1-methyl-3-(2-phenylethyl)imidazolium-chloride (6a) are deprotonated ina mixture of ammonia and THF by means of 11 mmol of NaH. Removal of theammonia and filtration of the THF solution made up to 40 ml results in aclear, spectroscopically pure solution of1-methyl-3-(2-phenylethyl)imidazolin-2-ylidene (6).

¹³ C-NMR (100 MHz, d₈ -THF/THF external reference, δ in ppm): 214.2 (s,NCN); 140.3; 130.0; 129.5; 126.4 (Ph--C); 122.43; 122.34 (NCHCHN); 53.0(NCH₂); 39.2 (s, CH₃); 37.8 (CH₂ Ph).

Example 7 1,2-Bis(2-ethoxyethyl)imidazolin-2-ylidene (7)

A) Preparation of 1-(2-ethoxyethyl)imidazole (7a)

A Schlenk tube is charged with 5.5 g (52 mmol) of potassium imidazolidein 50 ml of THF. While stirring, 7.7 g (50 mmol) of 2-bromoethyl ethylether are added and the suspension is stirred for 4 hours, then warmedgently. After cooling, the reaction mixture is filtered and the solventis removed. Distillation in a high vacuum gives 7a as a colorlessliquid. The purity was checked by GC-MS. Only one fraction was observedhere.

Mass spectrum (GC-MS): m/e=140 ([M⁺ ],80), 96 ([M⁺ -CH₃ CH₂ OCH₂+H],78), 81 ([M⁺ -CH₃ CH₂ OCH₂ CH₂ ], 100), 59 (CH₃ CH₂ OCH₂ ⁺, 75), 41(85)

B) Preparation of 1,2-bis(2-ethoxyethyl)imidazolium chloride (7b)

7 g (45 mmol) of 2-bromoethyl ethyl ether are added to 4.5 g (39 mmol)of 1-(2-ethoxyethyl)imidazole in 50 ml of THF and the mixture isrefluxed for 12 hours. A second liquid phase forms. After cooling to 0°C., the solvent is decanted off and the residue is extracted three timeswith THF. Removal of the solvent under reduced pressure gives (7b) (7.2g, 75%) as a yellowish oil.

¹ H-NMR (400 MHz, 25° C., CDCl₃ δ in ppm): 9.91 (s, 1H, N₂ C--H), 7.53(d, J=1 Hz, 2H, CH), 4.50 (t, J=5 Hz, 4H, N--CH₂), 3.74 (t, J=5 Hz, 2H,NCH₂ CH₂), 3.44 (q, J=7 Hz, 4H, O--CH₂), 1.08 (t, J=7 Hz, CH₃).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 136.5 (N₂ C--H), 122.5 (NC--H),67.9 (N--CH₂), 66.4 (NCH₂ --CH₂), 49.8 (O--CH₂), 14/7 (CH₃).

Mass spectrum (FAB): m/e=505 ([M⁺ +M-Br], 2), 213)[M⁺ -Br], 100).

C) Preparation of 1,2-bis(2-ethoxyethyl)imidazolin-2-ylidene (7)

2.93 g (10 mmol) of 1,2-bis(2-ethoxyethyl)imidazolium chloride (7b) aredeprotonated as described above in a mixture of 20 ml of THF and 100 mlof NH₃ using 260 mg (10.8 mmol) of NaH. Only after the addition ofammonia does the yellow oil dissolve completely. The reaction iscomplete after only 30 minutes. After evaporating the ammonia, themixture is made up with THF to 40 ml and the resulting solution is usedfurther without further work-up.

D) Preparation of 1,3-bis(2-ethoxyethyl)imidazoline-2-thione (7c)

In a Schlenk tube, 80 mg (2.5 mmol) of sulfur are suspended in 10 ml ofdegassed THF. While stirring, 10 ml (2.5 mmol) of 0.25 M carbenesolution (7) are added dropwise and the reaction mixture is stirred for1 hour. The solvent is removed under reduced pressure, the residue isdissolved in methylene chloride and filtered. After concentrating themother liquor, the product can be obtained by slow cooling in the formof yellow crystals. Yield: 446 mg (84%).

¹ H-NMR (400 MHz, CDCl₃ δ in ppm): 6.75 (s, 2H, N--CH═). 4.16 (t, J=5.5Hz, 4H, N--CH₂), 3.63 (t, J=5.5 Hz, 4H, N--CH₂ CH₂), 3.39 (q, J=7 Hz,4H, O--CH₂), 1.08 (t, J=7 Hz, 6H, CH₃).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 161.2 (C═S), 117.7 (N--CH═), 69.2(N--CH₂), 66.3(NCH₂ CH₂), 47.7 (OCH₂), 14.9 (CH₃).

E) Preparation ofpentacarbonyl[1,3-(2'-ethoxyethyl)imidazolin-2-ylidene]tungsten (7d)

A Schlenk tube is charged with 880 mg (2.5 mmol) of hexacarbonyltungstenin 10 ml of degassed THF. While stirring, 10 ml (2.5 mmol) of 0.25 Mcarbene solution (7) are then added dropwise under a protective gasatmosphere and the reaction mixture is stirred for a few hours. Thesolvent is then removed under reduced pressure and anyhexacarbonyltungsten still present is sublimed off overnight at roomtemperature.

The residue is dissolved in methylene chloride and filtered. Afterconcentrating the mother liquor, the product can be obtained by slowcooling in the form of yellow crystals. Yield: 1.01 g (75%).

¹ H-NMR (400 MHz, CDCl₃ δ in ppm): 7.23 (NCH═), 4.38 (t, J=5 Hz, 4H,N--CH₂), 3.69 (t, J=5 Hz, 4H, N--CH₂ --CH₂), 3.49 (q, J=7 Hz, 4H, OCH₂),1.17 (t, J=7 Hz, 6H, CH₃).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 200.7 (J(¹⁸³ W--¹³ C)=125 Hz,W--CO), 197.9 (J(¹⁸³ W--¹³ C)=125 Hz, W(CO)₄), 178.6 (W--CN₂), 122.2(N--CH), 70.0 (N--CH₂), 66.8 (NCH₂ --CH₂), 52.7 (OCH₂), 15.0 (CH₃).

Mass spectrum (CI): m/e=536 ([M⁺ ], 6), 508 ([M⁺ -CO], 12), 480 ([M⁺-2CO], 6), 213 (M⁺ -W(CO)₅ ], 100).

Elemental analysis (in % by weight): Calculated: C 35.84 H 3.79 N 5.22 W34.28 Found: C 35.86 H 3.86 N 5.29 W 34.04.

Example 8 1-(2'-Diethylaminoethyl)-3-methylimidazolin-2-ylidene (8)

A) Preparation of 1-(2'-diethylaminoethyl)-3-methylimidazolium chloridehydrochloride (8a)

4.9 g (60 mmol) of N-methylimidazole are added to 8.6 g (50 mmol) of2-(diethylamino)ethyl chloride hydrochloride in 50 ml of absoluteethanol and the mixture is refluxed for 12 hours.

After the reaction is complete, the solvent is removed under reducedpressure and the residue is washed a number of times with THF. Thisgives the product (8a) as a white hygroscopic powder. Yield: 108 g(85%).

¹ H-NMR (400 MHz, DMSO-d₆ δ in ppm): 9.56 (s, 1H, C--H), 8.05 (m, 1H,H--C═), 7.79 (m, 1H, ═CH), 4.69 (t, J=6.5 Hz, 2H, N--CH₂), 3.84 (s, 3H,N--CH₃), 3.52 (t, 2H, J=6.5 Hz, 2H, CH₂), 3.08 (q, J=7 Hz, 4H, CH₂, 1.17(t, J=7 Hz, 6H, CH₃).

¹³ C-NMR (100 MHz, DMSO-d₆, δ in ppm): 141.8 (C--H), 127.7 (H--C═),126.4 (═C--H), 53.9 (imidazole CH₂), 50.7 (N--CH₂), 47.5 (imidazole-CH₂--CH₂, 39.9 (imidazole-CH₃), 12.8 (CH₃).

Mass spectrum (FAB): m/e=399 ([M⁺ +M-2 HCl-Cl], 18), 182 ([M⁺ -HBr-Br],100).

B) Preparation of 1-[(2-diethylamino)ethyl]-3-methylimidazolin-2-ylidene(8)

2.54 g (10 mmol) of 1-[(2-diethylamino)ethyl)-3-methylimidazoliumchloride hydrochloride (8a) are suspended in 20 ml THF. 100 ml ofammonia are subsequently condensed into this. 21 mmol of NaH are addedat -78° C. The colorless solution is stirred under reflux for about 1hour until gas evolution ceases. After removing the ammonia, the mixtureis made up with THF to 40 ml and the resulting 0.25 molar carbenesolution is used further without further work-up.

¹³ C-NMR (100 MHz, THF/CD₃ NO, δ in ppm): 210 (C:), 119.1 (H--C═), 118.5(═C--H), 53.9 (CH₂), 49.2 (CH₂), 46.8 (CH₂), 37.5 (N--CH₃), 11.9 (CH₃).

c) Preparation of 1-(2'diethylaminoethyl)-3-methylimidazoline-2-thione(8b)

Using a method similar to the preparation of1,3-bis(2-ethoxyethyl)imidazoline-2-thione (7c), 80 mg (2.5 mmol) ofsulfur are admixed with1-(2'-diethylaminoethyl)-3-methylimidazolin-2-ylidene solution (8). Thisgives (8b) (478 mg, 89% of theory) as a yellow oil.

¹ H-NMR (400 MHz, CDCl₃ δ in ppm): 6.63 (d, J=2.5 Hz, 1H, H--C═, 6.49(d, J=2.5 Hz, 1H, H--C--) 3.86 (t, J=6 Hz, 2H, imidazole-N--CH₂), 3.37(s, 3H, N--CH₃), 2.53 (t, J=6 Hz, 2H, imidazole-N--CH₂ CH₂), 2.33 (q,J=7 Hz, 4H, N--CH₂), 0.76 (t, J=7 Hz, 6H, CH₃).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 161.4 (C═S), 117.3 (H--C═), 116.7(H--C═), 51.0 (imidazole-N--CH₂), 46.9 (imidazole-N--CH₂ CH₂), 45.9(N--CH₂), 34.5 (N--CH₃), 11.6 (CH₃).

Mass spectrum (GC-MS) m/e=213 ([M⁺ ], 13), 141 ([M⁺ -NEt₂ ], 13), 113([M⁺ -C₂ H₄ NEt₂ ], 8), 99 ([M⁺ -NC₂ H₄ NEt₂ ], 100), 86 (99), 71 (59),56 (41), 42 (31).

D) Preparation of chloro(η⁴-1,5-cyclooctadiene)]1-(2-diethylaminoethyl)-3-methylimidazolin-2-ylidene]rhodium(8c)

200 mg (0.4 mmol) of bis[(μ-chloro)(η⁴ -1,5-cyclooctadiene)rhodium] areinitially charged in 5 ml of THF and, while stirring, slowly admixedwith 3.3 ml (0.8 mmol) of a freshly prepared solution of1-(2-diethylaminoethyl)-3-methylimidazolin-2-ylidene (8). After 1 hourat room temperature, the solvent is removed under reduced pressure andthe residue is taken up in dichloromethane and filtered.

Removal of the solvent under reduced pressure gives (8c) as a yellowoil. Yield: 281 mg (81%).

¹ H-NMR (400 MHz, CDCl₃, δ in ppm): 6.93 (d, J=1.6 Hz, 1H, H--C═), 6.72(d, J=1.6 Hz, 1H, ═C--H), 4.95 (m, 2H, COD--CH), 4.69 (m, 1H,imidazole-CH₂), 4.29 (m, 1H, imidazole-CH₂), 4.00 (s, 3H, N--CH₃), 3.29(m, 1H, COD--CH), 3.18 (m, 1H, COD--CH), 2.97 (m, 1H, imidazole-CH₂--CH₂), 2.75 (m, 1H, imidazole-CH₂ --CH₂), 2.60 (m, 4H, N--CH₂, 2.35 (m,4H, COD--CH₂), 1.95 (m, 2H, COD--CH₂), 1.8 (m, 2H, COD--CH₂), 1.06 ("t",J=7 Hz, 6H, CH₃).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 182.2 (d, J(Rh--¹³ C)=49.5 Hz,C--Rh), 121.5 (H--C═), 121.2 (═C--H), 98.37 (COD--CH), 98.1 (COD--CH),68.1 (COD--CH), 67.3 (COD--CH), 53.8 (imidazole-CH₂), 49.0(imidazole-CH₂ --CH₂), 47.5 (N--CH₂), 37.5 (imidazole-CH₃), 33.3(COD--CH₂), 32.4 (COD--CH₂), 29.1 (COD--CH₂), 28.3 (COD--CH₂), 12.0(CH₃).

Example 9 1-(2'-ethylaminoethyl)-3-methylimidazolin-2-ylidene (9)

A) Preparation of 1-(2'-ethylaminoethyl)-3-methylimidazolium chloridehydrochloride (9a)

4.0 g (60 mmol) of N-methylimidazole are added to 7.7 g (50 mmol) of2-ethylaminoethyl chloride hydrochloride in 50 ml of absolute ethanoland the mixture is stirred for 36 hours at not more than 40° C. Ifhigher temperatures are used, elimination takes place and the1-methylimidazolium chloride thus formed can be removed only withdifficulty. After the reaction is complete, the solution is concentratedunder reduced pressure and the product is precipitated with ether.Washing a number of times with THF gives the product as a whitehygroscopic powder. Yield: 9.3 g (83%).

¹ H-NMR (400 MHz, DMSO-d₆ δ in ppm): 9.31 (s, 1H, N₂ C--H), 7.85 (m, 1H,N--CH), 7.71 (m, 1H, N--CH), 4.62 (t, J=6 Hz, 2H, imidazole-CH₂), 3.82(s, 3H, N--CH₃), 3.38 (t, J=6 Hz, 2H, imidazoleCH₂ --CH), 2.91 (q, J=7Hz, 2H, N--CH₂) 1.21 (t, J=7 Hz, 3H, CH₃).

¹³ C-NMR (100 MHz, DMSO-d₆ δ in ppm): 139.2 (N₂ CH), 125.4 (N--CH),124.1 (N--CH), 47.1 (imidazole-N--CH₂), 46.7 (N--CH₂ CH₂), 43.8(N--CH₂), 37.5 (N--CH₃), 12.4 (CH₃).

Mass spectrum (FAB): m/e=343 ([M⁺ +M-Cl -2HCl], 18), 154 ([M⁺ -Cl HCl],100).

Elemental analysis (in % by weight): Calculated: C 42.48 H 7.16 N 18.66Cl 31.49 Found: C 41.97 H 7.55 N 18.59 Cl 30.77.

B) Preparation of 1-(2-ethylaminoethyl)-3-methylimidazolin-2-ylidene (9)

2.26 g (10 mmol) of l-(2-ethylaminoethyl)-3-methylimidazolium chloridehydrochloride are dissolved in 20 ml of acetonitrile. 100 ml of ammoniaare condensed into this.

20 mmol of NaH are added at -78° C. Gas evolution commences immediately.The colorless solution is stirred for about 1 hour under reflux untilgas evolution ceases. After removing the ammonia, the mixture is made upwith acetonitrile to 40 ml and the resulting 0.25 molar carbene solution(9) is used further without further work-up.

¹³ C-NMR (100 MHz, CH₃ CN/CD₃ NO, δ in ppm): 210.5 (C:), 120.8 (CH═),120.6 (CH═), 51.4 (imidazole-N--CH₂), 51.2 (imidazole-NCH₂ --CH₂), 44.4(N--CH₃), 37.9 (N--CH₂), 15.6 (CH₃).

C) Preparation of 1-(2-ethylaminoethyl)-3-methylimidazoline-2-thione(9b)

320 mg of sulfur are added to the reaction mixture and the reactionvessel is shaken well. After 1 hour, insoluble salts are filtered offand the solvent is removed under reduced pressure. This gives (9b) as abrown oil.

¹ H-NMR (400 MHz, CDCl₃ δ in ppm): 6.72 (d, J=2.5 Hz, 1H, H--C═), 6.60(d, J=2.5 Hz, 1H, H--C═) 4.07 (t, J=6 Hz, 2H, imidazole-N--CH₂), 3.50(s, 3H, N--CH₃), 2.91 (t, J=6 Hz, 2H, imidazole-N--CH₂ --CH₂), 2.59 (q,J=7 Hz, 2H, N--CH₂), 2.30 (bis, 1H, NH), 0.99 (t, J=7 Hz, 3H, CH₃).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 162.0 (C═S), 117.4 (H═C--), 117.3(H--C═), 47.7 (imidazole-N--CH₂), 47.6 (imidazole-N--CH₂ CH₂), 43.6(N--CH₂), 34.9 (N--CH₃), 14.9 (CH₃).

Example 10 1,3-Di(S)-1'phenylethyl]imidazolin-2-ylidene (10)

A) Preparation of 1,3-di[(S)-1'-phenylethyl]imidazolium chloride (10a)

11.9 g (100 mmol) of (S) -1-phenylethylamine are initially charged in100 ml of toluene. While stirring vigorously, 3.0 g (100 mmol) ofparaformaldehyde are added. Warming of the reaction mixture is preventedby means of a water bath. After 30 minutes at room temperature, theflask is cooled to 0° C. using an ice bath and a further 11.9 g (100mmol) of (S)-1-phenylethylamine are added. While cooling and stirringvigorously, 30 ml (100 mmol) of a 3.3 molar HCl solution are slowlyadded dropwise. The cooling is then removed, 145 ml (100 mmol) of 40%strength aqueous glyoxal solution are slowly added and the reactionmixture is stirred overnight at 35-40° C.

For the work-up, 100 ml of ether and 50 ml of saturated sodium carbonatesolution are added. If necessary, the emulsion which forms is broken byaddition of a little pentane. The ether phase is separated off, theaqueous phase is washed three times with 100 ml each time of ether anddried under reduced pressure. The residue is taken up in 150 ml ofdichloromethane, dried over MgSO₄ and filtered.

Removing the solvent under reduced pressure leaves a yellow oil which iswashed a number of times with diethyl ether. This gives the product 10aas a slightly yellowish, very hygroscopic powder. Yield: 24.5 g (79%).The NMR spectra display only one set of signals, hence it can beconcluded that isomerization does not take place.

¹ H-NMR (400 MHz, CDCl₃ δ in ppm): 11.02 (s, 1H, N₂ C--H), 7.37 (m, 2H,phenyl-CH), 7.28(s, 2H, N--CH), 7.21 (m, 3H, phenyl CH), 5.52 (q, J=7Hz, 2H, R₃ C--H), 1.88 (d, J=7 Hz, 6H, CH₃).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 137.9 (N₂ CH), 135.9 (p-phenyl-CH),129.1 (phenyl-CH), 129.0 (CR₃), 126.8 (phenyl-CH), 120.5 (N--CH), 59.5(N--CH--Ph), 20.45 (CH₃).

Mass spectrum (FAB): m/e=589.2 ([M⁺ +M-Cl], 4.14), 277 ([M⁺ -Cl], 100),173 (13.6), 105 (43.8).

B) Preparation of 1,3-di[(S) -1'-phenylethyl]imidazolin-2-ylidene (10)

3.12 g (10 mmol) of 1,3-di-(S)-1'-phenylethylimidazolium chloride (10a)are deprotonated in accordance with the general description in a mixtureof 20 ml of THF and 100 ml of NH₃ using 260 mg (10.8 mmol) of NaH. Thesubstrate is sparingly soluble and only during the course of thereaction does a clear yellow solution form. After removing the ammonia,the mixture is made up with THF to 40 ml and the solution thus obtainedis used further without further work-up.

¹³ C-NMR (100 MHz, THF, CD₃ NO, δ in ppm): 211.2 (C:), 144.3(phenyl-CR), 128.3, (phenyl-CH), 127.1 (p-phenyl-CH), 126.6 (phenyl-CH),117.8 (N--CH═), 59.5 (N--CH) 22.3 (CH₃).

C) Preparation of 1,3-di[(S)-1'-phenylethyl]imidazole-2-thione (10b)

In a Schlenk tube, 80 mg (2.5 mmol) of sulfur are suspended in 10 ml ofdegassed THF. While stirring, 10 ml (2.5 mmol) of 0.25 M carbenesolution (10) are added dropwise and the reaction mixture is stirred for1 hour. The solvent is removed under reduced pressure, the residue isdissolved in methylene chloride and filtered. After concentrating themother liquor, the product can be obtained by slow cooling in the formof colorless crystals. Yield: 690 mg (89%).

¹ H-NMR (400 MHz, CDCl₃, δ in ppm): 7.3-7.1 (overlapping multiplets,10H, Ph--CH), 6.53 (s, 2H, ═C--H), 6.30 (q, J=7 Hz, 2H, CH), 1.66 (d,J=7 Hz, 6H, CH₃).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 161.6 (C═S), 140.0 (Ph--CR), 128.41(Ph--CH), 27.35 (p-Ph--CH), 126.6 (Ph--CH), 114.3 (═CH), 54.7 (CH), 19.1(CH₃).

Elemental analysis (in % by weight): Calculated: C 73.99 H 6.54 N 9.08Found: C 74.06 H 6.51 N 9.14.

D) Preparation ofpentacarbonyl{1,3-di[(S)-1'-phenylethyl]imidazolin-2-ylidene}tungsten(10c)

A Schlenk tube is charged with 880 mg (2.5 mmol) of hexacarbonyltungstenin 10 ml of degassed THF. While stirring, 10 ml (2.5 mmol) of 0.25Mcarbene solution (10) are added dropwise and the reaction mixture isstirred for a few hours. The solvent is removed under reduced pressureand any hexacarbonyltungsten still present is sublimed off overnight atroom temperature.

The residue is dissolved in methylene chloride and filtered. Afterremoving part of the methylene chloride under reduced pressure, theproduct can be obtained by slow cooling in the form of yellow crystals.Yield: 945 mg (63%).

¹ H-NMR (400 MHz, C₆ D₆ , δ in ppm): 7.14-7.29 (overlapping multiplets,10H, Ph--CH), 6.48 (g, J=3 Hz, 2H, N--CH--Ph), 6.28 (s, 2H, CH═), 1.55(d, J=6.5 Hz, 6H, CH₃).

¹³ C-NMR (100 MHz, C₆ D₆, δ in ppm): 200.9 (trans-CO), 198.5 (cis-CO),180.3 (CN₂), 141.2 (p-Ph--CN), 129.4(Ph--CH), 128.6 (Ph--CR), 127.1(Ph--CH), 120.4 (═CH), 60.9 (CH), 21.7 (CH₃).

E) Preparation of chloro(η⁴-1,5-cyclooctadiene){1,3-di[(S)-1'-phenylethyl]imidazolin-2-ylidene}rhodium(10d)

A Schlenk tube is charged with 200 mg (0.4 mmol) of bis[(μ-chloro)(η⁴-1,5-cyclooctadien)rhodium] in 5 ml of THF. To this solution, 3.3 ml(0.8 mmol) of carbene solution (10) are slowly added by means of asyringe.

The reaction mixture is stirred further for 1 hour at room temperature,the solvent is then removed under reduced pressure, the residue is takenup in methylene chloride and filtered. The complex is precipitated byaddition of pentane and washed with pentane. Removing the volatileconstituents under reduced pressure gives the complex as a yellowpowder. Yield: 327 mg (79%).

1H-NMR (400 MHz, CDCl₃ δ in ppm): 7.66-7.25 (overlapping multiplets,10H, Ph--CH), 6.91 (q, J=7 Hz, 1H, N--CH--Ph), 6.89 (q, J=7 Hz, 1H,N--CH--Ph), 6.82 (d, J=2 Hz, N--CH═), 6.65 (d, J=2 Hz, N--CH═), 5.06 (m,2H, COD--CH), 3.45 (m, 1H, COD--CH), 3.21 (m, 1H, COD--CH), 2.5-2.3 (m,4H, COD--CH₂), 2.2-1.8 (overlapping multiplets, 4H, COD--CH₂), 1.91 (d,J=7 Hz, 3H, CH₃, 1.83 (d, J=7 Hz, 3H, CH₃).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 182.0 (d, J(Rh--¹³ C)=51 Hz,Rh--CN₂), 142.2 (Ph--CR), 140.2 (Ph--CR), 128.8 (Ph--CH), 128.6(Ph--CH), 127.9 (p-PhCH), 127.6 (Ph--CH), 126.2 (Ph--CH), 125.8(p-Ph--CH), 118 (N--CH═), 118.2 (N--CH═), 98.5 (d, J(Rh--¹³ C)=7 Hz,COD--CH), 98.3 (d, J(Rh--¹³ C)=7 Hz, COD--CH), 68.7 (d, J(Rh--¹³ C)=14Hz, COD--CH), 67.5 (d, J(Rh--¹³ C)=14 Hz, COD--CH), 59.7 (N--CH), 58.2(N--CH), 33.0 (COD--CH₂), 32.7 (COD--CH₂), 28.7 (COD--CH₂), 22.8 (CH₃),20.8 (CH₃).

Mass spectrum (CI): m/e=522 ([M⁺ ], 38), 487 ([M⁺ -Cl], 100), 414 ([M⁺-COD], 22), 378 ([M⁺ -COD-Cl]), 277 (8), 137 (10).

Example 11 1-Methyl-3-(2-diphenylphosphinylethyl)imidazolin-2-ylidene(11)

A1) Preparation of 1-methyl-3-(2-diphenylphosphorylethyl)imidazoliumiodide (11a)

13.2 g (49.9 mmol) of 2-chloro-1-diphenylphosphorylethane are, withaddition of 7 ml (50 mmol) of triethylamine, reacted in a mixture of 50ml of toluene and 30 ml of ethanol with 3.4 g (50 mmol) of imidazole.The mixture is refluxed for 5 hours. The resulting1-imidazole-2-(diphenylphosphoryl)ethane is quaternized at roomtemperature with 3.13 ml (50 mmol) of methyl iodide.1-methyl-3-(2-diphenylphosphorylethyl)imidazolium iodide is precipitatedby addition of 100 ml of diethyl ether and dried under reduced pressure.This results in 15.7 g (65%) of (11a) as the monoethanol adduct.

1H-NMR (400 MHz, CDCl₃, δ in ppm): 8.9 (s, 1H, NCHN); 8.0-7.0 (m, 12H;Ph, NCHNCH); 4.5 (m, 2H, NCH₂); 3.6 (s, 3H, NCH₃); 3.2 (m, 2H, CH₂ PO);3.6; 1.1 (EtOH).

¹³ C-NMR (100.6 MHz, CDCl₃, δ in ppm): 136.68 (s, NCHN); 131.72 (d,J_(CP) =3 Hz), 131.4 (s); 130.10 (d, J_(CP) =9 Hz), 128.35 (d, J_(CP)=12 Hz, Ph), 122.66; 122.63 (s, NCHNCH); 43.43 (s, NCH₂); 36.31 (s,NCH₃); 29.97 (d, ¹ J_(CP) =69 Hz, CH₂ PO); 50.0; 17.9 (EtOH). ³¹ P-NMR(161.9 MHz, CDCl₃, δ in ppm): 28.47 (s).

Elemental analysis (C₁₈ H₂₀ N₂ P₁ O₁ I₁) (in % by weight): Calculated: C49.3 H 4.6 N 6.4 I 29.0 Found: C 47.8 H 4.7 N 6.1 I 29.0.

A2) Reduction of 1-methyl-3-(2-diphenylphosphorylethyl)imidazoliumiodide (11a) to 1-methyl-3-(2-diphenylphosphoethyl)imidazolium iodide(11b)

10.0 g (22.8 mmol) of 1-methyl-3-(2-diphenylphosphorylethyl)imidazoliumiodide (11a) in 50 ml of toluene are admixed with 20 ml (11.2 g, 97mmol) of methyldichlorosilane and 10 ml of ethanol and heated at 140° C.for 48 hours. After cooling, the organic phase is decanted off, thewhite solid is washed with 20 ml of toluene and 20 ml of pentane anddried under reduced pressure. This results in 9.2 g of (11b).

1H-NMR (400 MHz, CDCl₃ δ in ppm): 9.8 (s, 1H, NCHN); 7.5-7.0 (m, 12H;Ph, NCHNCH); 4.4 (m, 2H, NCH₂); 3.95 (s, 3H, NCH₃); 2.8 (M, 2H, CH₂ P).

¹³ C-NMR (100 MHz, CDCl₃, δ in ppm): 137.5 (s, NCHN); 132.2 (d), 129.2(s); 128.6 (d), 127.9 (d, Ph), 123.4; 122.2 (s, NCHNCH); 47.2 (d, ²J_(CP) =20 Hz, NCH₂); 36.5 (5, NCH₃); 28.8 (d, ¹ J_(CP) =8 Hz, CH₂ P).³¹ P-NMR (161.9 MHz, CDCl₃, δ in ppm): -19.8 (s).

B) Preparation of1-methyl-3-(2-diphenylphosphinoethyl)imidazolin-2-ylidene (11)

As described in the general example, 10 mmol of the salt (11b) obtainedunder point 11A2) are deprotonated in a mixture of ammonia/THF by meansof 11 mmol of NaH. Removal of the ammonia results in a spectroscopicallypure solution of the free1-methyl-3-(2-diphenylphosphinylethyl)imidazolin-2-ylidene (11) in THF.

¹³ C-NMR (100 MHz, THF/d₈ -THF external reference, δ in ppm): 217.3 (s,NCN); 132.1 (d), 129.4 (s); 128.6 (d), 127.6 (d, Ph), 122.3; 121.3 (s,NCHNCH); 48.2 (d, ² J_(CP) =20 Hz, NCH₂); 37.5 (s, NCH₃); 29.1 (d, ¹J_(CP) =18 Hz, CH₂ P). ³¹ P-NMR (161.9 MHz, THF/d₈ -THF externalreference, δ in ppm): 19.5 (s).

Example 12Bis-2,6-(3,3'-dimethyl-1,1'-dimethyleneimidazol-2-ylidene)pyridine

A) Preparation of bis-2,6-(1,1'-dimethyleneimidazole)pyridine

4.0 g (37.0 mmol) of potassium imidazolide (cf. Example 3A) aresuspended in 70 ml of toluene. 2.5 g (18.5 mmol) of2,6-bis(bromomethyl)pyridine are added at 0° C. and the mixture isallowed to warm to room temperature while stirring. After a totalreaction time of 12 hours, the mixture is freed of toluene under reducedpressure. To remove the potassium bromide, the residue is extracted anumber of times with chloroform. The extract is freed of the solvent ina high vacuum. The product remains. Yield: 3.76 g (85%).

1H-NMR (400 MHz, 25° C., D₂ O, δ in ppm): 7.72 (s, 2H), 7.53 (t, 1H),7.08 (m, 4H), 6.93 (d, 2H), 5.10 (s, 4H).

¹³ C-NMR (100 MHz, 25° C., D₂ O, δ in ppm): 155.9, 138.0, 137.8, 127.6,123.1, 120.3, 51.4.

B) Preparation of bis-2,6-(3,3'-dimethyl-1,1'-dimethyleneimidazoliumiodide)pyridine

3.5 g (14.6 mmol) of bis-2,6-(1,1'-dimethyleneimidazole)pyridine aredissolved in 20 ml of chloroform and admixed with 2.0 ml (32.0 mmol) ofiodomethane. After a further reaction time of 12 hours, theprecipitated, slightly yellowish solid is separated from the chloroformsolution by filtration and dried in a high vacuum. Yield: 7.24 g (88%).

¹ H-NMR (400 MHz, 25° C., D₂ O, δ in ppm): 8.67 (s, 2H), 7.81 (t, 1H),7.36 (m, 4H), 7.34 (d, 2H), 5.37 (s, 4H), 3.80 (s, 6H).

¹³ C-NMR (100 MHz, 25° C., D₂ O, δ in ppm): 153.24, 139.86, 136.88,123.70, 123.22, 123.06, 53.41, 36.07.

Elemental analysis (in % by weight): Calculated: C 34.44 H 3.66 N 13.39I 48.51 Found: C 34.20 H 3.59 N 13.44 I 48.76.

C) Preparation of bis-2,6-(3,3'-dimethyl-1,1'-dimethyleneimidazoliumhexafluorophosphate)pyridine

5.0 g (9.55 mmol) of bis-2,6-(3,3'-dimethyl-1,1'-dimethyleneimidazoliumiodide)pyridine are dissolved in 70 ml of water and admixed with 3.59 g(22.0 mmol) of ammonium hexafluorophosphate. The colorless precipitatewhich forms is filtered off and subsequently recrystallized from 70 mlmethanol. Yield: 5.11 g (78%).

¹ H-NMR (400 MHz, 25° C., DMSO, δ in ppm): 9.07 (s, 2H), 7.97 (t, 1H),7.65 (m, 4H), 7.45 (d, 2H), 5.51 (s, 4H), 3.88 (s, 6H).

¹³ C-NMR (100 MHz, 25° C., DMSO, δ in ppm): 153.57, 138.82, 137.18,123.38, 123.12, 122.00, 52.56, 35.83.

Elemental analysis (in % by weight): Calculated: C 32.21 H 3.42 N 12.52Found: C 32.28 H 3.36 N 12.40.

D) Preparation ofbis-2,6-(3,3'-dimethyl-1,1'-dimethyleneimidazol-2-ylidene)pyridine

5.59 g (10.0 mmol) of bis-2,6-(3,3'-dimethyl-1,1'-dimethyleneimidazoliumhexafluorophosphate)pyridine are dissolved in 15 ml of tetrahydrofuran.75 ml of ammonia are condensed in. 22 mmol of NaH are added at -78° C.The slightly yellowish solution is stirred under reflux for about 1 houruntil gas evolution has ended. The ammonia is subsequently allowed toevaporate. An immediate further work-up of the carbene solution isabsolutely necessary, since otherwise the solution quickly becomes redand a dark red solid begins to precipitate.

¹³ C-NMR (100 MHz, 25° C., THF, δ in ppm): 200.81, 157.10, 138.11,121.57, 120.50, 120.15, 55.05, 36.62.

Comparative Example Preparation of1,3-di-(S)-1'-phenylethylimidazolin-2-ylidene without addition ofammonia

3.12 g (10 mmol) of 1,3-di-(S)-1'-phenylethylimidazolium chloride aresuspended in 200 ml of THF. With exclusion of air, 260 mg (10.8 mmol) ofNaH and a spatula tip of potassium tert-butoxide are added. Slightevolution of gas occurs. As the reaction proceeds further, the NaHstarts to form lumps together with the starting material and thereaction stops. On slowly warming this suspension, the reaction mixturebecomes yellow and then brown. Significant constituents of the startingmaterial are still present as a lump on the bottom of the reactionflask. After stirring for 3 hours at 45° C., a sample of the reactionsolution is transferred with exclusion of air and moisture into an NMRtube with nitromethane-d₆ external reference and is examined by NMRspectroscopy. A complicated mixture of signals which cannot be assignedis observed.

Similar results are observed when the imidazolium salt is first boiledin THF until it is converted into a fluid oil and NaH is added onlythen.

Deprotonation using potassium tert-butoxide in acetonitrile leads to noappreciable conversion. An attempt to carry out the deprotonation usingNaH in acetonitrile results in secondary reactions by deprotonation ofthe acetonitrile which lead to a dark brown coloration of the reactionmixture.

We claim:
 1. A process for the preparation of a heterocyclic carbene ofthe formula ##STR5## wherein R¹, R², R³ and R⁴ are individually selectedfrom the group consisting of unsubstituted or substituted alkylidene of2 to 5 carbon atoms, unsubstituted or substituted alkylidine andalkylidyne of 2 to 5 carbon atoms, unsubstituted or substituted aryl ofof 6 to 14 carbon atoms and unsubstituted or substituted aralkyl of 7 to19 carbon atoms and R³ and R⁴ can be hydrogen or together with thecarbon atoms to which they are attached form a fused on a group of 5 to9 carbon atoms, the substituents being at least one member of the groupconsisting of halogen, --NH₂, --NO₂, --CN, isonitrile, --OH, ═O, --COOH,--CONH₂, pyridyl and azolyl, X is carbon or nitrogen with the provisothat R₃ is not present when X is nitrogen comprising reacting at -75° to0° C. in the absence of air and moisture an azolium salt of the formula##STR6## wherein R¹, R², R³ and R⁴ are defined as above and A isselected from the group consisting of halide, pseudohalide, borate,phosphate, carboxylate and metal complex ion with a deprotonation agentin pure liquid ammonia or pure alkylamine of 1 to 4 carbon atoms liquidat the reaction temperature or a mixture of pure ammonia and said purealkylamine and an organic polar aprotic solvent.
 2. The process of claim1 wherein R¹, R², R³ and R⁴ are individually selected from the groupconsisting of alkyl of 1 to 6 carbon atoms, alkylidene of 2 to 4 carbonatoms, alkylidyne of 2 to 4 carbon atoms, phenyl and phenylalkyl of 7 to10 carbon atoms.
 3. The process of claim 1 wherein one of R¹ and R² issubstituted with pyridyl or an azolium salt.
 4. The process of claim 1wherein the alkylamine is methylamine or ethylamine.
 5. The process ofclaim 1 wherein the reaction is effected at -50 to -30° C.
 6. Theprocess of claim 1 wherein the organic polar aprotic solvent is selectedfrom the group consisting of tetrahydrofuran, dimethylsulfoxide andacetonitrile and the volume ratio of ammonia and/or alkylamine to saidsolvent is 1:0.01 to 1:100.
 7. The process of claim 6 wherein the volumeratio is about 1:0.2.
 8. The process of claim 1 wherein thedeprotenation agent is selected from the group consisting of metalhydroxides, metal amides, metal alkoxides, methyl carboxylates,carbonylmetallates and hydrido(carbonyl)-metallates in an at leaststoichiometric amounts based on the compound of Formula II.
 9. Theprocess of claim 8 wherein the deprotonation agent is selected from thegroup consisting of sodium hydride and potassium amide in a 10% molarexcess based on the compound of Formula II.